1. Field of the Invention
This invention relates to a method for removing organic contaminants from aqueous compositions, and is particularly useful in the treatment of waste fluid.
2. Prior Art
One of the major problem facing cities, chemical manufacturers, and industries using various chemicals, is waste disposal. More particularly, cities and industries are often faced with the disposal of aqueous compositions containing organic contaminants. Regulations make it impossible to simply dump such waste water into streams, even if such method of disposal were desirable. Various methods have been proposed for removing such contaminants from waste water, but they have been relatively expensive or inefficient. Therefore, the removal of contaminants from aqueous compositions, and in particular from waste water containing small amounts of contaminants, is a problem which has not been completely solved.
More particularly, municipal water treatment for removal of trihalomethanes (THM's) resulting from the chlorination of drinking water and organic contaminants in ground water is a major problem for most water systems in the United States. Currently, no economically satisfactory methods exist for removal of such organic moieties.
The issue of trihalomethanes as a focal point of chlorinated (or more appropriately halogenated) organic substances in public water supplies has been continuing for the past several years. Hundreds of research and review papers have been published on the subject and conferences have been held on chlorination, some proceedings of which have been published by Ann Arbor Science.
Much concern about the production of trihalomethanes, notably chloroform, dichlorobromomethane, dibromochloromethane, and, to a lesser extent, bromoform, in the process of disinfecting of drinking waters has resulted in the inclusion of monitoring for these compounds in proposed Federal drinking water standards. Also, a standard of 100 ug/L total trihalomethanes has been proposed (annual average) as well as requirements for the use of activated carbon to control the formation of trihalomethanes. Final acceptance of the primary drinking water regulations has been delayed partly by legal action to which the American Water Water Works Association (AWWA) has played a major role in opposition to the promulgated regulations.
The AWWA has maintained that insufficient scientific evidence has been produced to justify the use of alternative disinfection technology relative to the attendant loss in consumer protection; or to justify the costs associated with the proposed technology, basically, activated carbon for precursor (natural organic matter in water which is known to yield THMs upon contact with aqueous chlorine) removal. This approach in turn, is projected to be more efficient than removal of THMs after production. While other prevention/removal techniques are possible, their present technological feasability is not fully demonstrated and the associated economics do not presently justify their use.
Still further, all surface water sources (i.e. lakes and rivers) and some groundwater employed for industrial as well as municipal purposes, contain a certain amount of naturally occurring organics, commonly referred to as "humics." This naturally occurring humic portion is further divided into a humic and a fulvic acid portion. These moieties are not well defined, but in general the humic acid is composed of high molecular weight organic acids and the fulvic is considered to be the low molecular weight fraction. The humic contained in natural waters presents two types of problems, one in the industrial sector, the other in the municipal drinking water area.
The problems associated with humics in industrial feed waters is related to their effect on the life time of anion exchange resins employed to soften boiler feed water. The anion exchange resins are extremely expensive; their fouling by humics increases operation costs significantly. There is, therefore, a need for a pretreatment to remove humics.
Further, chlorination of drinking water has long been a method used to prevent the transmission of disease from contaminated water. However, chlorination of waters containing bromide ion and natural organic compounds results in the production of chloro- and brom-organic compounds. It is now generally accepted that the chlorination of natural waters containing humic and fulvic acids produces not only volatile trihalomethanes (THMs), but also many other chlorinated aliphatic and aromatic compounds. The THMs are potentially carcinogenic compounds and the EPA has proposed a maximum level of 100 ug/L of total THMs in drinking waters. The toxicity of the less volatile halogenated organics has not been established; however, there has been concern over their potential activity.
Many different methods, such as macroreticular resins and granulated charcoal, have been tried to remove either the precursors of, or the halogenated organic compounds themselves, but such methods have only had limited success.
There exists numerous methods for removing organic contaminants from aqueous compositions, typically oil and water emulsions, see for example the following relevant U.S. Patents:
U.S. Pat. No. 2,367,384 to Tymstra; PA1 U.S. Pat. No. 2,937,142 to Rios; PA1 U.S. Pat. No. 3,196,619 to Shock; PA1 U.S. Pat. No. 3,487,928 to Canevari; PA1 U.S. Pat. No. 3,528,284 to Skoglund et al; PA1 U.S. Pat. No. 3,986,953 to Beaucaire; PA1 U.S. Pat. No. 4,231,866 to Moser et al; and PA1 U.S. Pat. No. 4,279,756 to Weiss et al PA1 U.S. Pat. No. 2,531,427 to Hauser; PA1 U.S. Pat. No. 2,966,506 to Jordan; PA1 U.S. Pat. No. 3,422,185 to Kuritzkef; PA1 U.S. Pat. No. 3,974,125 to Oswald; PA1 U.S. Pat. No. 4,081,496 to Finlayson; and PA1 U.S. Pat. No. 4,105,578 to Finlayson et al
More specifically, Tymstra describes a method for removing small quantities of water-immiscible organic oily impurities from water. The method consists of contacting the oily composition with an inert solid coated with a cation surface-active bonding agent. The solid employed may be beach sand, mud flat deposits, silt, clay, limestone, silica, rice hulls, etc. The cationic surface-active bonding agent may be quaternary ammonium, phosphonium, arsonium, or primary, secondary, or tertiary organic amines or salts thereof. This reference does not teach or suggest the use of the specific organoclays utilized herein to remove organic contaminants from aqueous compositions, nor the unexpected efficiencies of these clays.
Rios separates phenolic substances from aqueous solutions by contacting the aqueous solution with a clay adsorbent. The clay is previously treated by depositing carbonaceous material thereon, and then subjecting it to combustion regeneration to burn off the carbonaceous material.
Canevari separates droplets of oil from an aqueous phase, using a mixture comprising a sodium montmorillonite clay and an organic cationic agent or glycol. The organic cationic agent is preferably an amine. The mixture is applied as a flocculating clarifying solution containing from 1 to 5% of clay to water, and an effective amount of the organic cationic agent or glycol.
Beaucaire describes breaking an oil-water emulsion with waste-pickling acid solution, and thereafter converting the iron ions present in the waste-pickling solution to magnetite particles which absorb the oil. The magnetite particles and oil absorbed thereon are separated from the solution leaving a clarified solution.
Moser et al separates organic and aqueous phases by treatment of the emulsions with diatomaceous earth at an elevated temperature.
Weiss et al describes the use of a finely divided particulate mineral or clay material, the individual particles of which have been treated to produce a thin hydroxylated surface layer having a positive zeta potential at the adsorption pH.
None of the aforementioned references teach or suggest the use of organoclays to remove organic contaminants from water.
Additionally, organoclays are well-known in the art, see for example the following U.S. patents:
None of these aforementioned references teach or suggest the use of these organoclays to remove organic contaminants from water.